Which of the following is tetradentate ligand?

Trien is tetradentate ligand.

Tetradentate ligands are ligands with four donor atoms that can attach to the center meta atom or ion. Triethylenetetramine, as an example (abbreviated trien). Depending on their topology and the geometry of the metal center, tetradentate ligands attach through one of three connectivity's.

Hence, option C is correct.